There are surgical instruments in which the end-piece of a surgical object is drawn into the instrument during the course of an operation, until a thicker section of this object reaches the vicinity of an instrument head, whereupon the need arises to sever the end-piece of the object at the instrument head. Such instruments are used, in particular in minimally invasive surgery and in laparoscopy.
The surgical objects may be binding elements such as ligature binders or surgical suture material. There is for example a laparoscopic instrument which is introduced through a cannula (trocar sleeve) into the inside of the body, having a stretched ligature binder laid about an organ to be ligated, and transformed into a closed shape through insertion of its headpiece into its binding part. The end-piece of the ligature binder is then drawn into the inside of the instrument.
First, the headpiece of the ligature binder representing a thicker section, lays itself against the instrument head. Second, as the drawing-in of the end-piece continues, the binding part glides in the headpiece, whereupon the ligature binder narrows more and more. Third, a movement in an opposite direction is prevented by a pawl arranged in the headpiece, which pawl engages a toothing to which the binding part is provided. Finally, the ligature binder lies tightly enough about the organ. The end-piece of the binding part must now be cut off at the headpiece of the ligature binder. If a separate cutting instrument is used for this, having for example been introduced into the inside of the body through another cannula, this is awkward, and there is the risk of making the cut in the wrong place.
Known from WO 09/06725 is a laparoscopic instrument for the looping about of hollow organs and laying of endoligatures, which is introducible into the abdominal area through a cannula. In the case of this instrument, the base body of a ligature binder is fitted onto the distal end of the instrument head. The base body is provided with a continuous channel which runs in longitudinal direction of the instrument head. A belt-like, loop-shaped continuation connects with the distal end of the base body. The free end of the continuation is grasped by the operator with an additional auxiliary aid, laid about the organ which is to be ligated, and introduced into the channel. The free end of the belt-like continuation and the channel are provided with notched surfaces which correspond to each other and which prevent a release or loosening of the connection. On the inside of the instrument, the free end can be grasped by a gripping tool which is movable in longitudinal direction, in order to pull the ligature binder tight. In order to cut off the end-piece of the belt-like continuation in the inside of the instrument, a blade is provided which is to be actuated by the operator via the instrument shaft. Although this facilitates severance, the operator has no idea as to how tightly the ligature binder is lying about the organ. If it is sitting too tightly, this can have disadvantageous consequences for the organ; of it is sitting too loosely, it can become detached. This cannot be appraised with certainty by means of a visual inspection.